The ophthalmic artery (OA) is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges. Occlusion of the OA or its branches can produce sight-threatening conditions.

The OA emerges from the internal carotid artery usually just after the latter emerges from the cavernous sinus although in some cases, the OA branches just before the internal carotid exits the cavernous sinus. The OA arises from the internal carotid along the medial side of the anterior clinoid process and runs anteriorly passing through the optic canal with and inferolaterally to the optic nerve. Here, it should be noted that the ophthalmic artery can also pass superiorly to the optic nerve in a minority of cases.[1] In the posterior third of the cone of the orbit, the ophthalmic artery turns sharply medially to run along the medial wall of the orbit.

The central retinal artery is the first, and one of the smaller branches of the OA and runs in the dura mater inferior to the optic nerve. About 12.5mm (0.5 inches) posterior to the globe, the central retinal artery turns superiorly and penetrates the optic nerve continuing along the center of the optic nerve entering the eye to supply the inner retinal layers.

The OA then turns medially giving off 1 to 5 posterior ciliary arteries (PCA) that subsequently branch into the long and short posterior ciliary arteries (LPCA and SPCA respectively) which perforate the sclera posteriorly in the vicinity of the optic nerve and macula to supply the posterior uveal tract. In the past, anatomists made little distinction between the posterior ciliary arteries and the short and long posterior ciliary arteries often using the terms synonymously. However, recent work by Hayreh has shown that there is both an anatomic and clinically useful distinction.[2] The PCAs arise directly from the OA and are end arteries which is to say no PCA or any of its branches anastomose with any other artery. Consequently, sudden occlusion of any PCA will produce an infarct in the region of the choroid supplied by that particular PCA. Occlusion of a short or long PCA will produce a smaller choroidal infarct within the larger area supplied by the specific parent PCA.

The OA continues medially the superior and inferior muscular branches arise either from the OA or a single trunk from the OA subsequently divides into superior and inferior branches to supply the extraocular muscles.

The supraorbital artery branches from the OA as it passes over the optic nerve. The supraorbital artery passes anteriorly along the medial border of the superior rectus and levator palpebrae and through the supraorbital foramen to supply muscles and skin of the forehead.

After reaching the medial wall of the orbit, the OA again turns anteriorly. The posterior ethmoidal artery enters the nose via the posterior ethmoidal canal and supplies the posterior ethmoidal sinuses and enters the skull to supply the meninges.

The OA continues anteriorly, giving off the anterior ethmoidal artery which enters the nose after traversing the anterior ethmoidal canal and supplies the anterior and middle ethmoidal sinuses as well as the frontal sinus and also enters the cranium to supply the meninges.

Because of the obvious importance of the ocular globe, branches of the ophthalmic artery often are subdivided into two groups: those that supply the eyeball (ocular group) and those that supply non-ocular orbital structures (orbital group).[3]